In the case of rigid axles having direct air suspension, for example air-suspended rear axles on trucks, the bellows of the air suspension are arranged directly, thus immediately between the axle body of the rigid axle and a corresponding bellows receptacle on the vehicle chassis (for example on the frame longitudinal beam). Here, the bellows, due to the large volume thereof and the thusly associated large outer diameter, take up significant installation space between the axle body and the frame longitudinal beam.
For vibration damping, conventional rigid axles require at least one vibration damper on each side between the axle and the chassis, in addition to the spring elements formed by the bellows of the air suspension. The respective vibration damper is preferably arranged in the same region between the axle body and the chassis as the respective spring element of the axle, thus presently the bellows of the air suspension. Generally the vibration damper is arranged as far outside on the axle as possibly desired, in order to convert the deflection movements of the axle, or respectively the wheels, in a proportion as close to 1:1 as possible into corresponding damping movements of the vibration damper. Furthermore, for this purpose the vibration damper is ideally arranged parallel to the vertical axis of the vehicle.
However, this desirable arrangement of the vibration damper is problematic due to the large dimensions, or diameters, of the bellows of the air suspension because the respective air spring already takes up the greater part of installation space between the axle body and the chassis. With conventional air-sprung rigid axles it is therefore necessary to guide the vibration dampers past the air spring in a suitable manner.
Solutions are known for this purpose in which the vibration damper is fastened to the axle body and is guided obliquely past the air spring in the direction towards the corresponding vibration damper-fastening on the chassis. However the oblique passing of the vibration damper past the air spring leads to a strong tilting of the vibration damper—the vibration damper is not arranged parallel, but rather at an acute angle to the vertical axis. This degrades the efficiency of the vibration damper because the geometrically dependent damping path of the vibration damper (due to the tilting thereof) that is induced by the deflection movements of the wheel, or, respectively, the axle, is inevitably smaller than the respective deflection path of the wheel, or, respectively, the axle.
This means that more massive or stronger vibration dampers must be employed in order to maintain the same damping effect that would be offered by a slimmer vibration damper, which would be arranged substantially parallel to the deflection path, or, respectively, parallel to the air spring.
Other known proposals for solving the installation space problem between the air spring and the vibration damper consist in offsetting in parallel either the vibration damper or the air spring so that the vibration damper can be arranged in this manner either parallel to the deflection path, or, respectively, parallel to the air spring. Both, the measure of the parallel relocation of the vibration damper next to the air spring, as well as, alternative to this, the displacement of the air spring itself, is however constructively complicated and requires significant disadvantageous additional accommodations for the displaced vibration damper, or, respectively, the displaced air spring, which must be arranged on the axle body.